Perturbations of static pressure in a large-eddy simulation (LES) of air flow through vegetation exhibit a pattern characterized by a combination of high and low pressure. Over an x,z section chosen to pass through an ejection/sweep structure, the high pressure is centered at the intersection of the upper surface of the canopy and of a sloping scalar microfront. The high pressure extends to the ground and is followed by a zone of low pressure within the sweep region. Observations of static pressure at the soil surface in a forest support this picture.
Diagnostic analysis of the calculated pressures indicates that, of the four "components" of the pressure field, the mean-shear and the turbulent-turbulent terms are dominant. Contributions from canopy drag and subgrid-scale motions are each an order of magnitude smaller. Vertical profiles of the standard deviation of each of the pressure components show that mean-shear is the more important term inside the canopy, while the turbulent-turbulent term is the greater contribution above. The mean-shear term peaks at the canopy top because of the peak in the velocity gradient associated with the inflection in the mean velocity profile. In the x,z section, the mean-shear component appears to be vertically aligned, reflecting the vertical alignment in the w-velocity field. On the other hand, the turbulent-turbulent component exhibits a small downstream tilt, presumably characteristic of the turbulent velocity components from which it is constructed and which are aligned by the mean wind shear.